System of light control for



D.A. ROBERTS SYSTEM OF LIGHT CONTROL FOR SELENIUM CELLS Jan. 14, 1941..

Filed Aug. 30, 1959 Patented Jan. 14, 1941 UNITED STATES PATENT OFFICE SYSTEM OF LIGHT CONTROL FOR SELENIUM CELLS 2 Claims.

This invention relates to a system of light control for selenium cells. One of the objects of this invention is to provide light control means between a light source and a light sensitive cell, such as a selenium cell, whereby a beam of light originating from a light source and refracted or reflected to the selenium cell, may be intercepted at some convenient, accessible place on the surface of the receptacle or other object in which the light source and selenium cell are contained, whereby the weak current, which "is generated in the selenium cell by the beam of light thrown upon it, may be rendered inactive (while the light beam is cut off) and the relay or other instrument controlling the circuit for an electric device is closed temporarily, thereby enabling the controlled electrical device to function.

Light sensitive cells have been used in'a great many situations where the cells operate to open or close an electric circuit. One such embodiment is disclosed in my prior Patent No. 2,168,886 dated August 8, 1939, for Actuating means for typewriters and other mechanisms.

The present light control is capable of use in situations where manual control is required, such as the interposing of one finger or other object in a refracted or reflected beam of light.

Another object of the present invention is to provide means to control the direction in which it is desired to finally direct the light beam, whereby a plurality of the light control means may be grouped in close relation and the light sensitive cells may be similarly grouped.

Another object is to provide one or more light refracting or reflecting elements whereby a beam of light from the light source directed to the surface of a receptacle or wall may be bent across or through the surface and thence to the selenium .cell, whereby the beam of light may be intercepted at the surface to cut off the light from the selenium cell.

Another object is to eliminate moving and noisy parts in the light control element, and to prevent wear from operation, and from corrosion or other damage from arcing,

The invention may be used as a substitute for typewriter keys, linotype machine keys, etc. Its use will be found adaptable as a substitute for push buttons, inter-office signalling devices and in fact a great many situations where manual control for electric circuits is required.

The invention consists therefore in the provision of one or more prisms or other light refracting or reflecting elements interposed in a light beam issuing from a suitable light source, and arranged to direct the light beam from its light source to a light sensitive cell, whereby when the light beam is intercepted, as by placing one finger in the path of the light beam, the light sensitive cell becomes inactive and the relay circuit is broken, whereby the armature of the relay closes contacts of an electrical circuit for any electrically operated device.

The invention further consists in providing light control means at the surface of a receptacle or other object which contains the source of light and light sensitive cells, and placed in the path taken by the light beam, whereby manual operation will intercept the light beam and renderthe light sensitive cell inactive.

The invention further consists in the several novel features hereinafter fully set forth and claimed.

The invention is clearly illustrated in the drawing accompanying this specification in which Fig. 1 is a diagrammatic perspective view illustrating one embodiment of the invention.

Fig. 2 is a diagrammatic cross-sectional view illustrating an application of the invention to a plurality of the control systems.

Fig. 3 is a diagrammatic cross-sectional view illustrating a slightly modified form of the invention,

Fig. 4 is a front elevation showing the application of the light control as a substitute for a push button, and

Fig. 5 is a horizontal section taken on the line 5-5 of Fig. 4.

Referring to said drawing and first to Fig. 1, which illustrates a simple embodiment of the invention, the reference character l2 designates a light source such as an incandescent electric lamp and I3 designates a light sensitive cell, commonly known as a selenium cell. relay, M, are placed in circuit with the selenium cell and control the circuit I5 for any electrical device, such as a solenoid, magnet or other coil, for actuating some mechanical instrument. The light source and selenium cell may be contained in a cabinet or other receptacle or behind a wall or other closure, and in its present form the rays of light from the light source are projected to the surface of the object in which the light source and selenium cell are contained, or behind which they are located, and the beam of light is bent across or through the surface portion of the object and thence to the selenium cell, whereby a persons finger or any other object may be interposed in the path of the light beam across or through the surface portion to thereby intercept An amplifier A, and a V the light beam and render the selenium cell in active.

Interposed in the light beam at the surface of the object in which the apparatus is contained or behind which it is located is one or more light refracting or reflecting elements for bending the light beam back to the selenium cell, one form of which will now be described.

Located at any point at the surface of the object in which the apparatus is contained or behind which it is located, and in the path of light rays issuing from the light source, is a light refracting or reflecting element here shown in the form of a prism "5, which, together with a companion light refracting or reflecting element such as a prism l1, provide between them a space or gap in which the light beam may be intercepted by interposing a persons finger or other opaque object to thereby cut off the light beam to the selenium cell and render it inoperative, consequently permitting the relay to close the con.- tacts for the electric circuit controlled thereby.

For the purpose of illustration the prisms I6, I! are spaced apart a distance which allows a persons finger to be inserted in the space between them. A plate or other finger rest I8 is supported between and below or beyond the space between the prisms. To intercept a light beam a person places his finger on the-finger rest. Desirably the finger rest is bowed slightly along its major axis to conform somewhat to the cushion ofthe first joint of a persons finger. However, the finger rest may be made fiat or of any other desired contour. Between the light source and selenium cell is interposed a light shield [9 which prevents the direct rays of light issuing from the light source to impinge upon the selenium cell.

One or both prisms may be fixed against movement or they may be mounted so asto be adjustabl'e' around their axes and they may be mounted so that their axes may be adjusted angularly inany direction with respect to the axis of the companion prism. The purpose of this is to permit-the light beamto be bentand di rected at any desired angle whereby the associated selenium cell may be located wherever required. This is of especial advantage'where several of the light controls are grouped as'on a panel or grouped like the keys of a typewriter orlinotype machine, and where the associated selenium cells would be grouped in a somewhat confined space.

Fig. 2 shows a single light source I20. for activating two or more selenium cells [3a and individual light control means for the selenium cells associated therewith. Where several cells are grouped about a light source, light shields l9a should be interposed between the light source and the direct light rays that would fall upon the selenium cells from said light source. The

individual prisms lfia, Ila are located exteriorly of the wall Ila which encloses the light source and selenium cells. Openings lBa are provided The finger rest has an aperture lBc through which the light beam passes from one prism to the other. The light beam from the light source 12b to the selenium 13b is intercepted by placing ones finger or other object over the aperture I130. The light source and selenium cell may be covered by a wall llb with the finger rest interposed in a gap in the wall. A second aperture 180 in the wall .enables the light beam to pass exteriorly of the wall to the prism He at the light control station afiorded by the finger rest.

In Figs. 4 and 5 the light control is shown as applied as a substitute for a push button. The two prisms I60, I are mounted in a case lie with a gap or space between the prisms in which ones finger may be placed to intercept the light beam. The light source and selenium cell may be disposed'as illustrated in Fig. 1.

. ,It isto be understood that the prisms may take several forms, those shown being merely for the purposes of illustration. Furthermore the facets of one of the pair may be disposed at such angles to each other as to direct the beam of light where required, or a third prism may be provided with the facets thereof disposed so as to refract the light beam to the selected place.

From the above it is apparent-that there are no parts in the light control that are likely to wear out from usage; there are no parts that are noisy, no parts which must be moved. The light beam is intercepted by merely placing ones finger or other object in the path of the light beam. As a resultthe light control elements last indefinitely and are not subjected to injury from operation or from wear due to corrosion or arcmg.

I claim as new, and desire to secure by Letters Patent:

1. A system of light control for selenium cells comprising a light source and a selenium cell activated thereby, a closure therefor having openings one for the passage of a light beam projected from said light source to the exterior of the closure and one for the passage of the light beam from without to within the closure,

companion prisms, one arranged to refract a light beam projected from said light source, across the space between the prisms, and the other prism being arranged to refract the refracted light beam upon the selenium cell, the space between said prisms affording a control station where the light beam may be intercepted, whereby to render the selenium cell inactive, and an electric circuit controlled by said selenium cell.

2. A system of light control for selenium cells comprising a light source and a selenium cell activated thereby, a light shield between said light-source and selenium cell, a finger rest, companion prisms, one disposed at each side of the finger rest and one disposed in the path of a light beam projected from said light source, and arranged to refract the light beam across said finger rest to the other prism, said other prism being arranged to refract the refracted light beam upon the selenium cell, and an electric circuit controlled by said selenium cell.

DANIEL A. ROBERTS. 

